Portable lighting devices, such as flashlights, electric torches, electric lanterns, and/or the like have historically operated in a generally “digital” manner, in which the light is either fully on (i.e., at a full brightness level) or fully off (i.e., emitting no illumination). Various flashlights may have intermediate levels of illumination, however changes between each of these levels of illumination are generally very abrupt, without a noticeable transition period between the illumination levels. Light Emitting Diode (LED) flashlights are known to have particularly abrupt changes in illumination level, because LEDs do not include any filaments or ballast members that are required to heat up for full illumination, as may be the case for certain incandescent and fluorescent bulbs.
Abrupt changes in illumination levels such as those commonly associated with LED portable lighting devices as noted above, can be jarring to human eyes, which generally require a period of time to adjust to changes in illumination level. Thus, particularly when turning on or turning off a portable lighting device in a dark room, the user may experience a short period of impaired vision while the user's eyes adjust to the new illumination level.
The accommodation of human eye adjustment periods in portable lighting devices has historically been hindered by a number of portable lighting device-specific challenges. For example, the interchangeability of power supplies (e.g., batteries) having differing voltage and current output capabilities makes management of illumination levels in portable lighting devices challenging. Accordingly, a need exists for control mechanisms enabling desirable illumination level control for portable lighting mechanisms.